Do you know what problems will appear in etching process of flexible circuits? Ok, follow me to know the details:

1) Etching speed is geeting slower
This is usually because of the low temperature, low spray pressure or chemical proportion of etching solution. But if  these conditions under well control, the etching speed slow may be due to the dissolution copper content is too high. At this point, it is necessary to adjust the etching solution.
2) Precipitation appear in solution
This is due to lack of complexing agent Cl-, or the dilution caused by water. Precipitate is Cu2Cl2: insoluble in water.
3) Resist layer is damaged:
When excess acid is being, this phenomenon appeared. Especially in higher temperatures will appear. Now we can replaced by NaOH or water to adjust. If the acid concentration and the conditions are suitable, then the problem may be due to  improper cleaning of the board or exposure of flexible pcb.
4) The yellow residue in the copper surface
This residue is generally copper hydroxide, which does not dissolve in water. When the board is etched or alkaline cleaning to as the residue left on the board. In addition, when Cl-concentration and the acidity is too low in etching solution, after etched the white precipitate appeared on board, which may be insoluble Cu2Cl2 precipitation. Now we can use 5% hydrochloric acid solution to wash, and last wash by water.

When we know the above problems will appear in the etching process of flex circuits, so we will make the well quality controlling system to control these problems, and then ensure high quality flexible circuits, flex pcb.